RESUMO
BACKGROUND: To evaluate the effect of metformin on the plasma levels of rifampicin, isoniazid, and pyrazinamide in patients with drug-sensitive pulmonary tuberculosis being treated with first-line antituberculosis treatment (ATT) and to assess the influence of gene polymorphisms on the metabolic pathway of metformin and plasma levels of antitubercular drugs. METHODS: Nondiabetic adults aged 18-60 years with pulmonary tuberculosis were randomized to either the standard ATT (ATT group) or ATT plus metformin (METRIF group) groups in a phase IIB clinical trial. An intensive pharmacokinetic study with blood collection at 0 hour (predosing), followed by 1, 2, 4, 6, 8, and 12 hours after dosing was conducted during the first month of treatment in a subset of 60 study participants after a minimum of 14 doses. Plasma concentrations of rifampicin, isoniazid, pyrazinamide, and metformin were measured by high-performance liquid chromatography using validated methods, and pharmacokinetic parameters and OCT1 and MATE1 gene polymorphisms were compared between the groups. RESULTS: Significant increases in the clearance of rifampicin, isoniazid, and pyrazinamide were observed in patients in the METRIF group (n = 29) compared with those in the ATT group (n = 31). The AA genotypes of the single-nucleotide polymorphism of rs2289669 (MATE1) in the METRIF group showed a significantly decreased area under the concentration-time curve to the last observation point and increased clearance of rifampicin. CONCLUSIONS: Metformin altered rifampicin and isoniazid plasma concentrations in patients receiving antituberculosis treatment for pulmonary tuberculosis with little effect on sputum conversion at the end of treatment. Studies with larger sample sizes are needed to understand host drug-drug interactions.
RESUMO
BACKGROUND & OBJECTIVES: Concomitant feeding and anti-tuberculosis (TB) drug administration are likely to reduce nausea and enhance compliance to treatment. However, food could lower plasma drug concentrations. This study was undertaken to examine the effect of food on two-hour plasma concentrations of rifampicin (RMP), isoniazid (INH) and pyrazinamide (PZA), and pharmacokinetics of these drugs in adult TB patients. METHODS: Newly diagnosed adult TB patients were recruited from the Revised National Tuberculosis Control Programme (RNTCP) treatment centres in Chennai Corporation, Chennai, India. Two-hour post-dosing plasma concentrations were determined in 25 patients, and a semi-intensive pharmacokinetic study was undertaken in six patients. RMP, INH and PZA concentrations were determined by high-performance liquid chromatography. RESULTS: The geometric mean two-hour concentrations with food and under fasting conditions were 2.2 and 5.5 µg/ml for RMP (P<0.001), 3.9 and 11.3 µg/ml for INH (P<0.001), and 18.0 and 28.2 µg/ml for PZA (P<0.001), respectively. Drug administration with food caused the plasma concentration to decrease by 50, 45 and 34 per cent for RMP, INH and PZA, respectively. Significant decreases in peak concentrations and exposures of drugs and delay in time to attain peak concentrations of drugs when taken with food were also observed. INTERPRETATION & CONCLUSIONS: Our findings showed that food lowered anti-TB drug concentrations significantly and delayed absorption. Patients may be explained the beneficial effects of taking anti-TB drugs in a fasting state and advised to do so. There is a need for more research on optimization of dosing to maximize efficacy and safety of currently used drugs.
